Network load balancing (NLB) is a software-based windows load balancing solution provided by Microsoft. An NLB cluster allows a user to use two or more servers in combination to form one server cluster, which works like one server from the perspective of a client. Each server is also called an NLB node.
NLB working modes include a unicast working mode, a multicast working mode, and an Internet Group Management Protocol (IGMP) working mode. In the unicast working mode and the multicast working mode, the NLB node uses a cluster media access control (MAC) address for NLB communication. That is, a destination MAC address of a data packet sent by an Internet Protocol (IP) network to the NLB node is a cluster MAC address, and the cluster MAC address is not bound to a port. Consequently, a forwarding device broadcasts the data packet on all ports, which increases network traffic burdens.